Automatic control system for hoisting machine



P 1962 s. T. BUCK 3,053,344

AUTOMATIC CONTROL SYSTEM FOR HOISTING MACHINE Filed Sept. 15, 1958 5 Sheets-Sheet 1 or: on: V up 0 Q S-ro P 0 7! INVI- ZNTOR.

Jrsmvga TBucK,

RTTOQNEYS.

Sept. 11, 1962 s. T. BUCK 3,053,344

AUTOMATIC CONTROL SYSTEM FOR HOISTING MACHINE Filed Sept. 15, 1958 5 Sheets-Sheet 2 INVENTOR. Jrnmea TBUCK A T To Q N E Y5 c AUTOMATIC CONTROL SYSTEM FOR HOISTING MACHINE Filed Sef't. 15, 1958 S. T. BUCK Sept. 11, 1962 5 Sheets-Sheet 3 INVENTOR. J'rzwzwa Z'Buck, Wm 41 ATYORNEYS.

Sept; 11, 1962 s. T. BUCK 3,053,344

AUTOMATIC CONTROL SYSTEM F OR HOISTING MACHINE Filed Sept. 15, 1958 5 Sheets-Sheet 4 88 1 .96 I liazz 30 3,653,344 Patented Sept. 11, 1962 United States Patent Ofiice 3,053,344 AUTOMATIC CONTROL SYSTEM FOR HOISTING MACHINE Steward T. Buck, Buck Equipment Corporation 720 Anderson Ferry Road, Cincinnati 38, Ohio Filed Sept. 15, 1958, Ser. No. 761,186 7 Claims. (Cl. 187-2) My invention relates to hoisting machines and more specifically to an automatic control system for the lift platform or elevator of a hoisting machine.

In recent years hoisting machines have come into wide spread use in construction jobs and the like wherein supplies are elevated to different floor levels. Such hoisting devices fall generally into two categories, the first comprising towers which are erected on the building site by a crew of workmen, the tower and its component parts being assembled more or less piece by piece. The second type comprises portable hoisting towers which are mounted either on a truck or trailer and formed in hinged together sections which may be quickly raised and lowered. Essentially, the instant invention has been expressly designed for use with hoisting devices of the latter class, although its utility is not so limited and it may be readily used with the first type of tower or in any other hoisting device wherein substantially automatic operation is desired.

All prior art hoisting devices of which I am aware, irrespective of their type, have been manually controlled in that it is necessary for the operator to start and stop the lifting mechanism each time the lift platform or other lifting means is raised or lowered. With the operator at ground level, it is particularly difficult for him to accurately judge when the lifting platform is properly aligned with the level of a floor a number of stories above him. This results in considerable jockeying back and forth of the lift platform which is both time consuming and hard on the operating parts of the machine. Similarly, even if the platform is being lowered, the operator must stand by to disengage the operating mechanism when the platform reaches its lowermost position or some intermediate position of use, as where materials are being unloaded directly from a truck or the like onto the lift platform. Since in most instances the hoist operator has other duties, such as loading materials onto the lift platform, or bringing materials to the loading area, he can perform such other duties only when the hoisting machine is not in operation.

A principal object of the instant invention is to provide an automatic control system for hoisting machines which require a minimum of operator attention, thereby freeing the operator for other duties.

A further object of the invention is the provision of a control system which will automatically stop the lifting means at predetermined upper and lower positions, the operator having only to start the lifting means on its upward or downward journey, whereupon the control mechanism takes over to stop the lifting means at a preset position.

Still a further object of the invention is the provision of a control system incorporating improved hoisting mechanism and safety features which greatly enhance the versatility of the hoisting machine and at the same time assure positive accident free operation.

I The foregoing, together with other objects of the invention which will appear hereinafter or which will be apparent to the skilled worker in the art upon reading these specifications, I accomplish by that construction and arrangement of parts of which I shall now describe an exemplary embodiment.

Reference is now made to the accompanying drawings wherein:

FIGURE 1 is a side elevational view of a hoisting machine incorporating the invention.

FIGURE 2 is a side elevational view illustrating the machine in collapsed position.

FIGURE 3 is a schematic view illustrating the control panels for the system.

FIGURE 4 is a horizontal sectional view taken along the line 4-4 of FIGURE 1.

FIGURE 5 is a side elevational view of the mechanism illustrated in FIGURE 4.

FIGURE 6 is a vertical sectional View taken along the line 6-6 of FIGURE 5.

FIGURE 7 is a vertical sectional view taken along the line 7-7 of FIGURE 5.

FIGURE 8 is a horizontal sectional view taken along the line 8-8 of FIGURE 7.

FIGURE 9 is a vertical sectional view taken along the line 9-9 of FIGURE 5.

FIGURE 10 is a vertical sectional view taken along the line 10-10 of FIGURE 5.

FIGURE 11 is a vertical sectional view taken along the line 11-11 of FIGURE 4.

FIGURE 12 is an enlarged fragmentary plan view of the cable engaging pulley shown in FIGURE 11.

FIGURE 13 is a plan view with interior parts shown in dotted lines of the automatic stop mechanism for the lift platform.

FIGURE 14 is a vertical sectional view taken along the line 14-14 of FIGURE 13.

FIGURE 15 is a vertical sectional view taken along the line 15-15 of FIGURE 14.

FIGURE 16 is a fragmentary vertical sectional view taken along the line 16-16 of FIGURE 14.

FIGURE 17 is a wiring diagram of the control system.

FIGURE 18 is a wiring diagram of a simplified control system.

FIGURE 19 is a wiring diagram illustrating how the control panels of FIGURE 3 may be wired to the system.

Referring first to FIGURES 1 and 2 of the drawings, I have therein illustrated an exemplary portable hoisting machine with which the control system of the present invention may be employed. The device comprises a base or frame 1 mounting a vertically extending tower 2 along which a platform or other lifting means 3 is adapted to travel, the lift platform having grooved rollers 4 which move along the trackways 5 formed as integral parts of the tower structure. The life platform 3 is raised and lowered, as from the position shown in solid line to the position shown in dotted lines, by means of a cable 6 which extends upwardly from the drive unit 7 around a pulley mechanism 8 at the top of the tower and then downwardly for engagement with the lift platform. Preferably a two part cable will be employed.

In the embodiment illustrated, the base or frame 1 is provided with retractable wheels 9 by means of which the device may be readily transported from place to place; and to this end the tower is formed in a plurality of hinged sections 2a, 2b and 2c, as seen in FIGURE 2, so that it may be readily collapsed for movement from one site to another. Since the mechanism for erecting the tower does not constitute a part of the present invention, it will not be described in detail. Reference is, however, made to the recently isued Patent No. 2,653,685 dated September 29, 1953 and entitled, Portable Hoisting Tower, wherein the construction and mode of erecting and collapsing the tower structure are described in detail. As already indicated, the instant invention is concerned with the driving unit and its associated control for raising and lowering the lift platform, which unit will find utility in all types of hoisting machine.

Referring now to FIGURE 4 of the drawings, the drive unit comprises a prime mover which may be either an electric motor or an internal combustion engine, the drive shaft of which is shown at 11. A series of drive belts 12 connects the drive shaft of the motor to a transmission 13 enclosed in a housing 14 which also mounts clutch mechanism 15 and brake mechanism 16. The transmission 13 serves to drive the main shaft 17 which mounts a winch 18 for 'winding and unwinding the cable 6 which raises and lowers the lift platform. The shaft 17 also mounts a sprocket 19 connected by an endless chain 20 to the sprocket 21 forming a part of control mechanism 22 which automaticallly regulates the extent of upward and downward movement of the lift platform.

While not, strictly speaking, a part of the instant invention, the shaft 17 may also be provided at one end with a power take-off 23 operatively connected through suitable gear mechanism 24 to a winch 25 utilized to raise and lower the tower sections. Similarly, at its opposite end the shaft '17 may be provided with a work head 26.

Other operating components of the drive unit are a slack cable device 27 which acts to deenergize the control system should the cable become slack for any reason, and a torque bar arrangement 28 to adjust the tension of the drive belts 12 connecting the prime mover to the transmission.

Referring now to FIGURE 7, it will be seen that the main shaft 17 is driven by means of a bull gear 29 located Within the housing 14. The entire housing 14 is supported by the main shaft 17, being mounted thereon by means of ball bearings 30, the arrangement being such that the housing may pivot about the shaft 17. Such pivoting movement permits tightening or loosening of the drive belts 12 by varying the distance between the sheaves 31 on drive shaft 11 and sheaves 32 on clutch shaft 33 forming a part of the clutch mechanism 15. Pivotal movement of the housing 14 is controlled by means of the torque bar 28 which, as best seen in FIGURE 6, com prises a turn buckle 34 one end of which is connected through a swivel joint 35 to the transmission housing 14, and the opposite end of which is connected through a swivel joint 36 to the machine frame 37. By tightening or loosening the turn buckle 34, the entire transmission housing may be rocked about the shaft 17, thereby altering the distance between the sheaves 31 and 32 and hence altering the tension on the drive belts '12.

Referring now to FIGURES 5 and 9, the bull gear 29 is reversibly driven from clutch mechanism 15 which incorporates a down clutch 38 and an up clutch 39, both of which are electrically controlled and adapted to rotate the bull gear in opposite directions, depending upon the direction in which the shaft :17 is to be rotated. As seen in FIGURE 9, the clutch shaft 33, which is driven by drive belts .12, is journaled in housing 14 and an inner frame member 40. A first element 41 of electric clutch 42 is keyed to the shaft 33 and engageable, upon actuation, with a second element 43 secured to a gear 44 which is freely mounted on shaft 33 by means of ball bearings 45. The teeth of gear 44 mesh with the teeth of bull gear 29, as will be evident from FIGURE 5, so that upon actuation of the clutch 42, the elements 41 and 43 will coact to drive gear 44. When clutch 42 is deenergized, the driven shaft 33 will simply turn relative to gear 44, which remains stationary.

At its outermost end the shaft 33 mounts a gear 46 the teeth of which mesh with a mating gear 47 keyed to a shaft 48 which parallels shaft 33 and is journaled in the housing 14 and inner frame member 40. The shaft 48 mounts an electric clutch 42a which is identical to clutch 42 and has a first operating part 41a keyed to shaft 48 and a second element 43a secured to gear 49 which is freely rotatable on shaft 58. On energization of the clutch 420:, the shaft 48 will drive gear 49 which meshes with the bull gear 29.

With the arrangement just described, both the shafts 33 and 48 are driven at all times the machine is in operation, but the bull gear 29 will be driven only at such time as one or the other of the clutches 42, 42a is energized. This clutch arrangement has proven to be highly advantageous in that it operates smoothly and is instantaneously reversible.

The brake control for the winch is independent of the drive mechanism and, as seen in FIGURE 10, comprises an electro magnetic multiple disc spring brake which is normally set. That is, it is only upon energization of the brake mechanism that the winch is free to rotate. The winch is normally held against rotation by means of a gear 50 which is keyed to shaft 51, the gear 50 meshing with bull gear 29. A generally cup-shaped element 52 is also keyed to the shaft. This element contacts alternate discs of a set of disc 53 carried by stationary element 54 fixedly secured to the housing 55. A spring pressed plate 56, also fixed relative to the housing, normally bears against the discs 53, thereby holding them against rotation and, through the cup-shaped element 52, preventing rotation of the shafts 51. When the brake mechanism is energized, electro magnets 57 act to retract plate 56 against the compression of its springs 58, thereby releasing the discs 53 for rotation about the stationary element 54 and hence freeing the cup-shaped element and shaft for rotation.

As an additional safety feature when the lift platform is being lowered, the shaft 51 of the brake mechanism is connected to an over speed governor 58 which is a centrifugal device acting to automatically energize the up electric clutch 39 in the event a predetermined excessive speed is attained, thereby effecting an additional braking action on the bull gear.

Referring now to FIGURES 13 16, I have therein illustrated the control mechanism for automatically stopping the lift platform at predetermined upper and lower levels. As seen therein the sprocket 21 which, it will be remembered, is driven through chain 20 and sprocket 19 aflixed to main shaft 17, drives a threaded shaft 59 which is journaled at its ends in the casing of the device. In place of the sprocket arrangement shown, the shaft 59 may be gear driven from the main shaft 17. The threaded shaft mounts a pair of internally threaded members 60 and 61 each having a plurality of radially disposed teeth 62 arranged to be selectively engaged by a longitudinal guide bar 63 normally biased into engagement with the teeth by means of springs 64. When in its normally up or tooth engaging position, the bar 63 will hold the members 60 and 61 against rotation so that, as the shaft 59 rotates, the members 60 and 61 will move axially along the threaded shaft depending upon the direction of its rotation.

The control device preferably contains a set of three limit switches arranged to coact with the members 60 and 61, the switch 65 being a normally closed up switch and having an arm 66 adapted to be contacted and opened by member 60 as the member travels along the threaded shaft. Similarly, the switch 67 is a normally closed switch having an arm 68 arranged to be contacted and opened by the member 61. The switch 69 having arm 70 is a normally open switch and is also adapted to be contacted by the member 61. The switch 67 is the down switch, whereas the switch 69, which is arranged to be contacted slightly in advance of the switch 67, is a slow down switch.

The bar 63 carries a scale 71 on its front face by means of which the operator may set the members 60 and 61 in accordance with the desired stop levels of the lift platform. For example, if the maximum travel of the lift platform is from 0 to the scale 71 will be calibrated, left to right, from 0 to 150 for the member 60; and the rightmost end of the scale will also have a 0 5 position to indicate the point at which the member 61 will contact and close switch 67. It will be understood, of course, that the shaft 59 rotates in synchronism with the main shaft 17, and consequently for each revolution of the winch 18-which either reels in or pays out a given length of cablethe threaded members 60 and 61 will move along the shaft a proportional distance. In an exemplary embodiment wherein a two part cable is employed, the ratio of rotation between the winch 18 and the threaded shaft 59 is 1:2, with the pitch of the threads on the shaft 59 such that the members 60 and 61 will travel axially A for each 10" of platform movement or 20 of cable, the members 60 and 61 moving to the left, as seen in FIGURES 13 and 14, as the cable is wound onto the drum and moving to the right as it is played out.

In the exemplary setting down in FIGURE 14, the member 60 is set to contact and open up switch 65 when 150' of cable has been wound on the winch. As the threaded shaft 59 rotates to move the member 60 to the left for contact with the switch 65, the member 61 will move a like distance to the left so that the member 61 will subsequently travel to the right for contact with down switch 67 as the threaded shaft is rotated in the opposite direction upon unwinding movement of the winch to return the lift platform to the lowermost position.

If, for example, the lift platform is to be raised only 50' then the guide bar 63 would be depressed, thereby freeing the member 60 for rotation, and the member would be advanced along the shaft 59 until its leading edge coincided with the 50' mark on the scale. When in this position, the member 60 will contact the arm of switch 65 when 100 of cable has been wound on the winch (assuming a two part cable). As seen in FIG- URES l4 and 16, the guide bar 63 may be conveniently provided with pins 72 at its opposite ends engageable by hooks 73 effective to lock the guide bar in depressed position, thereby permitting the threaded members 60 and 61 to be readily rotated relative to the shaft. Critical or close adjustment of the threaded members can be obtained by rotating them through only one or two of the notches 62. For example, in the exemplary embodiment illustrated, the notches 62 are on 30 centers and their relation to the pitch of the screws is such that each notch represents 2" of platform movement. In other words, each adjusting revolution of the members 60, 61, results in a 2 variation in platform height.

Adjustment of the down or lower position of the platform is made by bringing the lift platform to the desired down positionwhich may be anywhere between -l50'and with the platform so positioned rotating the member 61 until it coincides with the 0 at the right end of the scale 71.

The switch 69, which is a slow down switch, is adapted to be contacted andclosed by the members 61 in advance of the time it contacts the stop swicth 67. This switch will be contacted when the lift platform is from 5 to feet from its lower limit and will serve to reduce the speed of the motor driving the winch, thereby slowing down the lift platform as it approaches its lowermost position. The function of the slow down mechanism will be best understood from the following discussion of the overall operation of the device. This switch is optional and may be eliminated if desired. Of course, if desired a fourth switch could be installed to act as a slow down as the lift reaches its upper limit.

Reference is now made to FIGURE 17 of the drawings wherein an exemplary control circuit for the various operating components of the device is illustrated. The circuit includes a source of power 74 which may be either a storage battery or a current rectifier, if A.C. current is available. In either event, the control system will comprise an On-Off switch 75 which, as seen in FIGURE 3, may be conveniently made a part of an operator control panel 76 mounted at any convenient place adjacent the drive unit, the panel including a stop button 77, andup and down buttons 78 and 79, respectively. I also prefer to provide a second control panel 76a which may be secured to the tower 2 at any desired position. This panel has a stop button 77a and up and down buttons 78a, 79a arranged in series with their counterparts on panel 76. The panel 76a may be conveniently positioned adjacent an upper floor level so that a workman removing material from the lift platform may control the device in the event the operator on the ground is busy with other duties.

Referring again to the exemplary wiring diagram of FIGURE 17, when either of the up buttons is pushed to initiate upward movement of the lift platform, a circuit is formed through the normally closed up switch 65 of control mechanism 22 and normally closed relay 80, thereby energizing relay coil 81. The coil 81 serves to close relays 82, 83, 84, and up switch by-pass relay 84a, and it opens normally closed realy 85. The relay 82 form a circuit to throttle solenoid 86 and the coil 87 of timed delay relay 88. As seen in FIGURE 5, the solenoid 86 is connected to the throttle 89 which controls the speed of prime mover 10 and serves to advance the prime mover from idling speed to full operating speed. The time delay relay 88 does not close for a matter of seconds after the initial energization of coil 87, thereby permitting the motor to attain full operating speed; but when it does close, it energizes coil 90 which closes relays 91 and 92, the former acting through previously closed relay 83 to energize normally set brake 16, thereby releasing the drive mechanism, and at the same time relay 92 completes the circuit to up clutch 38 to drive the main shaft 17 and winch 18.

When the lift platform reaches its predetermined upper level, the normally closed up switch 65 is opened, thereby breaking the circuit to coil 81 and opening relay 84 which acts to deenergize clutch relay 84 and brake relay 83.

When either of down switches 79, 79a is closed, a circuit is formed to coil 93 which acts to close relays 94 and 95. At the same time relay 96 is closed to energize and release brake 16, as is relay 97 which energizes throttle solenoid 86 and time delay coil 87. The coil 87 functions as before to close relays 91 and 92, thereby completing the circuit to the down clutch through relay 94. The normally closed relay 80 in the up clutch circuit is also opened, thereby locking out the up clutch 38.

As the lift platform approaches its lowermost position, slow down switch 69 in the control device is closed to energize coil 98 which closes relay 99 and opens normally closed relay 100, the latter relay serving to break the circuit to throttle solenoid 86 and thereby release throttle 89 for movement to the idle position. This effectively reduces the speed of the lift platform as it approaches its lowermost position. As the lift platform reaches the lowermost position, the switch 67 will be opened, thereby breaking the circuit to coil 93 which opens relays 94 and to deenergize down clutch 39 and also opens relay 96 to deenergize and hence set brake 16.

It will be apparent that either the up or down circuit can be broken by pressing either of the stop buttons 77, 77a or upon opening of overspeed switch 101 or slack cable switch 102. The overspeed switch will be opened by the overspeed governor 58 (FIGURE 10) in the event the mechanism runs at a predetermined excessive speed.

The mechanism controlling the slack cable switch 102 is shown in FIGURES 4, 1'1 and 12, wherein it will be seen that the switch 102 is adapted to be opened by a plunger 103 spring press toward the switch by spring 104 but normally maintained out of contact therewith by pulley wheel 105 engaged by the lift platform cable 6. When the cable is taut, it presses against the pulley and compresses spring 104, thereby maintaining the plunger 103 away from switch 102. However, should the cable break or become slack for any other reason, the force of the taut cable against the pulley 105 will be released, and the spring will move the plunger into contact with switch 102 thereby opening it and breaking the drive circuit.

As best seen in FIGURE 11, the slack cable device is mounted on a column 106 pivotally received in sleeve 107 mounted to the machine frame, the arrangement being such that the slack cable device may pivot in a horizontal plane to follow the cable 6 as it travels across the winch. As shown in FIGURE 12, I prefer to mount the pulley 105 in a closed yoke 108 pivoted at 109 to a base block 110, the yoke having a latch 111 by means of which it may be opened to readily reengage the cable.

From the foregoing description, it should be apparent that the proposed device provides an essentially automatically acting lifting device requiring operator control only to start the lift platform on its upward or downward movement, as the case may be. The device is extremely versatile and is adjustable over a wide range of operating levels.

While I have disclosed my invention in a preferred embodiment, various modifications may be made without departing from the spirit and purpose of it, and consequently I do not intend to be limited excepting in the manner set forth in the claims which follow. As a specific example of a modification, the up switch 65, down switch 67 and slow down switch 69 could be adjustably mounted on the tower structure for actuation by the lift platform itself, as it travels along the tower, rather than by employing the control mechanism 22. Such an arrangement would, however, require that the position of the switches be changed with each change in operating conditions-which would be more time consuming than simply adjusting the members 60 and 61 in the control device 22.

In FIGURE 18, I have illustrated a simplified control system particularly suited for use with an internal combustion engine. In this embodiment the control system is wired through the motor generator 110 so that current is supplied to the system only when the engine is running. Should the engine stop for any reason-as by running out of fuelthe generator will no longer supply current to the control system. This will have the effect of setting the brake 16 which, it will be remembered, is a normally set brake.

As before, the control system contemplates up switches 78, 78a and down switches 79, 79a, together with stop switches 77, 77a which may be arranged on the control panels 76 and 76a. When either of the up switches is closed, a circuit is formed through normally closed up switch 65, normally closed relay 80, thereby energizing relay coil 81. In this instance, however, the coil serves to directly close relay -111 to energize and hence release brake 16. At the same time relay 112 is closed to actuate throttle 86 and relay 113 serves to energize the up clutch 38 to drive the winch 18. At the same time, the normally closed relay 85 locks out the down clutch mechanism. When the lift platform reaches the upper limit, the limit switch 65 will be opened thereby breaking the circuit controlling the up clutch and brake and throttle.

In similar fashion, when either of the down switches 79, 79a are closed, the limit switch 67 and relay 85 form a circuit to coil 93 which closes relays 114, 115 and 116, thereby releasing the brake, actuating the throttle solenoid and energizing the down clutch 39.

In this embodiment the overspeed limit switch 101 is a normally open switch and arranged to form a circuit to up clutch 38 in the event the lift platform attains an excessive speed during its downward travel. The circuit also includes a resistor 117 which provides a partial voltage drop so that full power is not applied to the up clutch component. With this arrangement the partial power applied to the up clutch causes it to exert a braking action on the bull gear and hence serves to slow down its speed of rotation and hence the rate of descent of the platform.

In FIGURE 19, I have illustrated a simplified circuit by means of which the control panel 76a may be connected to the main control panel 76, the connection being effected by means of a plug-in jack 118. It will be obvious that more than one remote control panel may be conveniently provided if desired.

The foregoing modifications are exemplary of those which can be made without departing from the spirit and purpose of the invention. Similarly, it will be understood that the bull gear employed to drive the winch could be replaced by a worm gear adapted to be driven from a second shaft to which the clutch component are operatively connected. In such event, one of the clutch components could be geared to the second shaft with the remaining component connected to the shaft by a sprocket and chain, thereby providing a simple reversing drive for the second shaft.

Having thus described the invention in certain exemplary embodiments, what I desire to secure and protect by Letters Patent is:

1. In drive mechanism for a hoisting machine having a vertically movable lifting means which is raised and lowered by a winch and cable, a main shaft mounting the said winch, clutch means operatively connecting said shaft to a motor having an idle speed and an operating speed, said clutch means comprising an up and down element for rotating the said shaft and winch in opposite directions so as to raise and lower the lifting means, means for selectively engaging said up and down clutch elements, and control means for automatically stopping said lifting means at a predetermined up position, said control means including means operative, when the lifting means reaches the predetermined up position, to disengage said up clutch element and to reset said brake means, said control means also including means operative, when said down clutch element is engaged, to engage said up clutch to effect a braking action on said winch should said winch attain a predetermined excessive speed.

2. In drive mechanism for a hoisting machine having a vertically movable lifting means raised and lowered by a winch and cable, a main shaft mounting said winch, clutch means operatively connecting said shaft to a motor having an idle speed and an operating speed, said clutch means comprising an up component and a down component, brake means normally holding said shaft against rotation, the improvements which comprises control means for selectively raising and lowering said lifting means, said control means including manually actuated means for selectively initiating engagement of said up and down clutch components, time delay means operative upon the actuation of the said manually actuated means to effect engagement of the selected clutch component after a predetermined time delay, said time delay means also acting to release said brake means concurrently with the engagement of the selected clutch component, means responsive to the actuation of the said manually actuated means for advancing said motor from idle speed to operating speed prior to the engagement of the selected clutch component, and means for automatically disengaging said clutch components in accordance with predetermined vertical positions of said lifting means, said last named means including means operative, when the lifting means has reached its predetermined position, to set said brake means and return said motor to idle speed.

3. In drive mechanism for a hoisting machine having a vertically movable lifting means raised and lowered by a winch and cable, a main shaft mounting said winch, clutch means operatively connecting said shaft to a motor having an idle speed and an operating speed, said clutch means comprising an up component and a down component, brake means normally holding said shaft against rotation, the improvement which comprises control means for selectively raising and lowering said lifting means, said control means including manually actuated means for initiating engagement of said clutch components, time delay means operative upon the actuation of said manually actuated means for effecting engagement of the selected clutch component after a predetermined time delay, said time delay means also acting to release said brake means concurrently with the engagement of the selected clutch component, means responsive to the actuation of said manually actuated means for advancing said motor from idle speed to operating speed prior to the engagement of the selected clutch component, means for automatically disengaging said clutch components in accordance with predetermined vertical positions of said lifting means, said last named means including means operative, when the lifting means reaches predetermined up or down positions, to set said brake means, means etfective when said limting means reaches the predetermined up position to return the motor to idle speed, and means operative upon down movement of the lifting means to return the motor to idle speed in advance of the lifting means reaching the down position, whereby to retard the speed of the lifting means in advance of its reaching down position.

4. The device claimed in claim 3 wherein said clutch components include electro magnetic clutch members, wherein said brake means comprises an electro magnetic brake, wherein said control means includes a control circuit for energizing said electro magnetic clutch and brake members, and wherein the manually actuated means for initiating engagement of said clutch components comprises switch means forming a part of said control circuit.

5. The device claimed in claim 4 wherein the means for automatically disengaging said clutch components comprises limit switches forming a part of said control circuit, said limit switches being incorporated in a control device having a threaded shaft rotated in timed relation to the movement of said main shaft, wherein the said threaded shaft mounts a pair of threaded member movable axially along said threaded shaft upon rotation thereof, and wherein said threaded members are adapted to contact and actuate said limit switches as said threaded shaft is rotated.

6. The device claimed in claim 5 wherein the means acting upon down movement of the lifting means to return the motor to idle speed in advance of the lifting means reaching the down posit-ion comprises a third limit switch mounted for contact by one of said threaded members as it moves along said threaded shaft.

7. In drive mechanism for a hoisting machine having a vertically movable lifting means raised and lowered by a winch and cable, a main shaft mounting said winch, a bull gear fixed to said shaft, clutch means operatively connecting said bull gear to a motor having an idle speed and an operating speed, said clutch means comprising an up component and a down component, an electro magnetic brake means normally holding said bull gear against rotation, the improvement which comprises a clutch housing pivotally mounted on said shaft and surrounding said bull gear, said clutch housing mounting said up and down clutch components, each of said components comprising a clutch shaft having a gear thereon in engagement with said bull gear, said last named gears being rotatable relative to their shafts, an electro magnetic clutch member mounted on each of said clutch shafts, said electro magnetic clutch members each having a first element fixed to one of said last named gears and a second element fixed to the shaft on which it is mounted, said electro magnetic clutch members, upon energization, acting to connect each clutch shaft to the gear thereon, means connecting one of said shafts to said motor, a drive gear fixed to said last named shaft in meshing engagement with a drive gear connected to the other of said shafts, whereby said second shaft is powered from the first, control means for selectively raising and lowering said lifting means, said control means including manually actuated means for initiating engagement of the selected clutch component, time relay means operative upon the actuation of said manually actuated means to energize said electro magnetic clutch member controlling the selected clutch component after a predetermined time delay, said time delay means acting to energize said electro magnetic brake means concurrently with the energization of the selected clutch component, means responsive to the actuation of said manually actuated means for advancing said motor from idle speed to operating speed prior to the energization of said electro magnetic clutch member, and means for automatically de-energizing said electro magnetic clutch members in accordance with predetermined vertical positions of said lifting means, said last named means including means operative, when the lifting means reaches its predetermined position, to reset said brake means and simultaneously return said motor to idle speed.

References Qited in the file of this patent UNITED STATES PATENTS 1,586,768 Allen Jan. 1, 1926 1,601,346 Callahan Sept. 28, 1926 1,651,569 Wilson Dec. 6, 1927 2,001,674 Erickson May 14, 1935 2,068,948 Freeman Jan. 26, 1937 2,085,504 'Mc-Dill June 29, 1937 2,165,993 Young July 11, 1939 2,386,392 Fike Oct. 9, 1945 2,566,824 Carlson Sept. 4, 1951 2,581,887 Saxton Jan. 8, 1952 2,646,965 Addicks July 28, 1953 

